Modern sea lamprey control pits technology against the invaders
After 100 years of coordinated effort, 98% of all Great Lakes sea lamprey has been eliminated, according to the Great Lakes Fisheries Commission, the organization responsible for managing invasive species within the basin.
Unfortunately, the remaining 2% is enough to start the cycle again if left unchecked, and current technology “does not make complete eradication possible,” said Marc Gaden, director of communications and legislative liaison for the Fisheries Commission. Great Lakes.
Researchers at the Royal Ontario Museum in Toronto agree that every sea lamprey is unlikely to be removed from the Great Lakes.
“Chasing this last pair of lamprey, even if it were possible, would be incredibly difficult and expensive,” Gaden said.
In 1955, when Canada and the United States established the Great Lakes Fisheries Commission to manage sea lamprey invasion, reaching 98% elimination was inconceivable. At that time, the sea lamprey decimated the Great Lakes fishery and the Commission was tasked with finding ways to curb or limit its numbers.
Since then, billions have been invested in research and management efforts. By developing and implementing a variety of control methods, the Commission has not only kept the invasive sea lamprey under control, but has virtually eliminated it from the Great Lakes, and new control technologies may one day offer the possibility. to finish with the last 2%.
The GLFC has an interactive online tool that can show the status of sea lamprey populations in each lake per year.
Developing a chemical control agent that was harmful to sea lamprey but not lethal to native species was one of the first goals of the Great Lakes Fisheries Commission.
“It’s easy to kill fish, but it’s very difficult to kill only the fish you’re looking for,” Gaden said.
The lamprey is now the main tool used to control sea lamprey in the Great Lakes. Artificial pesticide was first tested in Lake Superior in 1958. In 1986, it was used in tributaries of the five Great Lakes, according to an article in the Journal of Great Lakes Research.
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Lampricide 3-trifluoromethyl-4-nitrophenol (TFM) targets sea lamprey larvae in their nursery habitat with the goal of preventing them from reaching adulthood. Gaden said about 120 tributaries of the Great Lakes are treated on a rotating basis with lampricides.
Sea lamprey-producing streams do not need to be treated with lampricide every year.
“When we deal with a current, we kill classes for three or four years at a time, and then we don’t have to go back to that current for a few years,” Gaden said.
TFM is lethal to sea lamprey because they have low levels of the enzymes needed to remove the chemical from their body. Other organisms are generally not affected by TFM, according to the Great Lakes Fisheries Commission’s website. Bayluscide is a newer and less expensive additive that is used during some treatments to reduce the amount of TFM needed.
Not all stakeholders are comfortable with the widespread application of pesticides in the Great Lakes watershed.
In the late 1990s, advocates of lake sturgeon raised concerns about the impact of lampricide on sturgeon larvae. Lake sturgeons use the same spawning habitat as the sea lamprey, and both species spawn at the same time of year.
In response to these concerns, a new set of lampricide application guidelines called the Sturgeon Protocol was established. As part of the criteria for the Sturgeon Protocol, the application of lampricide is restricted to rivers where lake sturgeons spawn.
“We are pushing for measures to protect the sturgeon population and we take it very seriously,” Gaden said.
Many environmental groups also oppose the use of lampricide. A current petition to change.org calls for a moratorium on lampricide treatments in Vermont to protect mud puppies.
Mud puppies are an aquatic salamander, often called a bioindicator because of their sensitivity to pollutants. In 2016, the Michigan Department of Natural Resources added mud to the list of species of concern due to declining populations. Mud puppies are one of the native species vulnerable to lampricide.
Gaden said the commission understands the public’s concern about the collateral damage caused by pesticide use in the Great Lakes. He said the commission is continuously funding research into alternative methods to reduce the amount of lampricide used each year.
“Our goal is not to rely solely on one pesticide safely,” Gaden said. He said successful management “depends on several techniques working together instead of putting all the eggs in one basket.”
Physical barriers such as dams were the first control measures used to manage the invasion of sea lamprey. These early barriers had several flaws. In addition to limiting access to rivers for desirable native species, they were not always effective in stopping sea lamprey. During spring flood events, lamprey can sometimes prevent prey.
“If your barrier is letting something pass, it’s not as effective,” Gaden said.
Barriers continue to play an important role in sea lamprey management, Gaden said. But modern designs, such as bottom catches, allow the passage of jumping fish while limiting access to the sea lamprey. Fish ladders are stepped corridors that also allow jumping fish to move upstream while limiting the lamprey.
Unfortunately, these barriers also restrict the ability of native fish species that do not jump to move upstream.
In some places, trap paths and classifications are used to help fish that do not jump. But catching and moving fish are labor-intensive processes reserved for selected species.
“It’s not optimal, but there are some cases where we will physically move the real important fish,” Gaden said.
Physical barriers such as prey are an enigma to fishing managers and invaders. Barriers disrupt river connectivity, which is detrimental to many native species. The dams offer some financial incentives. Gaden said the barriers are cost-effective because a single building expense can provide 50 to 100 years of protection. They also significantly reduce the amount of lampricide needed each year.
Thousands of dams in the Great Lakes Basin have eliminated the need to apply lampricide to thousands of miles of tributaries, although the growing popularity and benefits of dam removal could jeopardize it.
“If we had to treat all the streams in the Great Lakes basin, we basically couldn’t afford to do that,” he said.
One form of marine lamprey control uses natural pheromones and alarm signals. These natural compounds are classified as biopesticides, which the U.S. EPA considers less toxic to the environment.
During spawning, the lamprey releases pheromones that attract other adults to the nest site. While “alarm signals emanate from dead or injured sea flashes and warn other sea lampreys of imminent danger, triggering a flight response,” according to the Great Lakes Fisheries Commission’s website.
“We’ve invested a lot of time and considerable money in developing this,” Gaden said. “And now we have pheromones registered in the EPA as a biopesticide.”
Potentially, a push-pull application can be useful in controlling sea lamprey movements. Pheromones and alarm signals could be used to lure adult sea lamprey into traps, move them away from inappropriate spawning habitat, move them to areas that are easy to treat with lampricides, or repel them. of areas where control tactics are difficult to implement.
Genetic research has made possible the previously unthinkable prospect of Great Lakes-free Great Lakes, but it would require a significant investment of time, resources and public support.
“We’re talking billions of dollars in R&D and probably a 20-year commitment,” Gaden said. “Obviously, we don’t embark lightly and without completely thinking about where we’re going.”
Researchers know that genetic editing of lamprey is possible.
An example of genetic manipulation would be to alter the genetic code of the sea lamprey so that they produce only male offspring but not females. Without any reproductive females, the population would eventually die.
“We have a lot of questions to ask, both from a science perspective about where you’re going, where you invest your money in this research, but also when it comes to the ethical side,” Gaden said. “Because every time it’s about genetic manipulation, there are also ethical issues that need to be resolved.”
After more than 100 years, ongoing research and new technologies may one day offer the ability to completely eliminate all Great Lakes sea lamprey and, with them, the need to apply pesticides.
“It’s only limited by the imagination of engineers and biologists,” Gaden said.
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Featured image: invasive sea lamprey (photo credit: Great Lakes Now)